1. Field of the Invention
Embodiments of the present invention relate to a patterning method, and more particularly, to a mold structure which can realize a conformal contact by applying a voltage between a mold structure and a material layer positioned in opposite to each other, so as to prevent defective patterns, and a patterning method using the aforementioned mold structure and a method of fabricating an LCD device with the aforementioned mold structure.
2. Discussion of the Related Art
A fine-pattern formation process, for example, a process for forming an electric circuit is an important element which can determine the efficiency and capacity of device as well as a main element which can affect the properties of device.
Recently, there have been various efforts to improve the efficiency and capacity of device, and more particularly, studies and researches in relation with the formation of fine pattern so as to improve the efficiency and capacity of device.
The fine-pattern formation process is necessary for flat panel display devices such as a printed circuit board (PCB), a liquid crystal display device (LCD), and a plasma display panel (PDP).
Various studies for formation of the pattern have been made, especially, a photolithography process using a photoresist is most generally used, which will be described as follows.
First, a photoresist layer having photosensitivity is coated on a metal layer, wherein the metal layer is formed on a substrate of a semiconductor material or an insulation material such as glass.
Then, a soft baking process is applied to the photoresist layer.
After an exposure mask having a light-transmission region and a light-shielding region defined therein is positioned above the photoresist layer, UV rays are applied to the photoresist layer through the exposure mask. Generally, the photoresist may be classified into a positive type and a negative type. For convenience of explanation, the case using the negative type photoresist will be explained.
If UV rays are irradiated to predetermined portions of the negative type photoresist, the predetermined portions of the negative type photoresist, which are irradiated with the UV rays, are changed on their chemical structure.
Then, if the negative type photoresist is dipped into a vessel filled with a developer, a photoresist pattern is formed by removing the remaining portions of the negative type photoresist which are not irradiated with the UV rays.
Subsequently, after blocking some of a metal layer with the photoresist pattern, it is dipped into the developer. Then, a hard baking process is applied thereto, and then the metal layer except the portion below the photoresist pattern is etched to thereby form a metal pattern.
According as the photoresist pattern is removed by a stripper, only the metal pattern remains on a substrate.
At this time, a semiconductor layer, an insulation layer or other conductive layers instead of the metal layer may be etched.
However, the related art fine-pattern formation method using the photoresist has the following disadvantages.
First, the process becomes complicated due to the resist coating, the soft and hard baking for the coated resist, and the exposure and development.
Also, the fabrication cost is increased. In general, the process for the electric device including a plurality of patterns (or electrodes) is provided with a first photoresist step to form one pattern and a second photoresist step to form another pattern. This means that the expensive resist process line is required between each of the pattern lines. Thus, the fabrication cost for the electric device is increased.
Third, it may cause environmental contamination. Since the resist coating is generally performed by spin coating, the amount of resist disused on the coating process is increased, whereby it may cause the environmental contamination as well as the increasing fabrication cost.
Fourth, there are the defective devices. When forming a resist layer by the spin coating, it is difficult to control the precise thickness of resist layer. Accordingly, the thickness of resist layer is not uniform so that un-stripped resist portions remain on the surface of the pattern formed, thereby causing the defective devices.
In order to overcome the problems of the above-mentioned patterning method using photolithography, a new patterning method using an In-Plane soft mold will be explained as follows.
First, a master is prepared so as to obtain a predetermined shape in a surface of a soft mold by an embossing or depressed pattern.
For example, a primary layer is formed by depositing an insulation material such as silicon nitride Si3N4 or silicon oxide SiO2 on an insulation substrate such as silicon substrate. Then, a photolithography process is applied to the primary layer, whereby the primary layer is formed as a desired pattern.
At this time, the above-mentioned pattern of the insulation substrate may be formed of metal, photoresist or wax as well as silicon nitride or silicon oxide. Through the above-mentioned process, the master is completed.
On completion of the master, a pre-polymer layer is formed on the master.
Then, the pre-polymer layer is cured.
Next, the cured pre-polymer layer is referred to as a soft mold. As the soft mold is stripped off from the master, the embossing and depressed pattern is formed in the surface of the soft mold.
The soft mold is used to form a micro-unit fine pattern (pattern formed by the embossing or depressed shape of the soft mold). For example, the soft mold may be used for a color filter of a color filter substrate or an electrode of an OLED device.
The soft mold may be fabricated by curing an elastic polymer, for example, PDMS (polydimethylsiloxane).
The soft mold may be applied to various fields of soft lithography, soft molding, capillary force lithography and In-Plane printing.
If using the soft mold of PDMS, the modulus of mold is below 5 Mpa. In this case, even though the thickness of mold coated is thin, it is possible to obtain the conformal contact capacity. This soft mold may react on the material layer being in contact, whereby the reliability of mold is lowered. In order to prevent the reliability of mold from being lowered, a hard type material having a high hardness is used for the mold.
Hereinafter, a patterning method using a related art mold will be described with reference to the accompanying drawings.
FIG. 1A is a cross section view of illustrating a patterning method using a mold structure according to the related art. FIG. 1B is a plane view of illustrating a pattern shrinkage generated when forming a pattern by a related art mold.
As shown in FIG. 1A, for example, a mold 20 having embossing and depressed shapes formed in its surface is brought into contact with a pattern-formation layer 14, whereby predetermined patterns corresponding to the embossing and depressed shapes of the mold 20 are formed in the pattern-formation layer 14.
In FIG. 1A, a light-shielding layer 11, red, green and blue color filter layers 12a, 12b and 12c, and an overcoat layer 13 are formed on a substrate 10. Thereon, the pattern-formation layer 14 is coated to form column spacers. In this case, after the pattern-formation layer 14 is brought into contact with the mold 20, they are cured so that the column spacers (not shown) are formed in the pattern-formation layer 14 by the depressed shape of the mold 20.
However, if the mold 20 is in the hard type, the mold 20 is not elastic due to its property. At this time, if the hard-type mold 20 is brought into contact with the pattern-formation layer 14 which is coated thinly, the depressed shape of the mold 20 is not conformed with the pattern-formation layer 14, whereby the depressed shape of the mold 20 comes off the pattern-formation layer 14. As shown in FIG. 1B, the corners of the pattern-formation layer 14 may shrink inward so that the contact failure may occur.